Converting Lymphoma Cells into Potent Antigen-Presenting Cells for Interferon-Induced Tumor Regression

Development of a targeted IL-12 immunotherapy platform for B-cell lymphomas

Immunotherapy has emerged as a promising approach to cancer treatment that utilizes the potential of the immune system to precisely identify and eradicate cancerous cells. Despite significant progress in immunotherapy, innovative approaches are required to enhance the effectiveness and safety of these treatments. Interleukin-12 (IL-12), widely recognized for its essential function in immune responses, has been explored as a potential candidate for treating cancer. However, early attempts involving the systemic administration of IL-12 were ineffective, with significant adverse effects, thus underscoring the need for innovation. To address these challenges, we developed a therapeutic molecule that utilizes a single-chain IL-12 mutant (IL-12mut) linked to a tumor-targeting arm. Here, we describe the development of a highly effective IL-12-based TMEkine™ platform by employing a B-cell lymphoma model (termed CD20-IL-12mut). CD20-IL-12mut combined the attenuated activities of IL-12 with targeted delivery to the tumor, thereby maximizing therapeutic potential while minimizing off-target effects. Our results revealed that CD20-IL-12mut exhibited potent anticancer activity by inducing complete regression and generating immunological memory for tumor antigens. Collectively, our data provide a basis for additional research on CD20-IL-12mut as a potential treatment choice for patients with B-cell lymphomas such as non-Hodgkin's lymphoma.

IRF8-mutant B cell lymphoma evades immunity through a CD74-dependent deregulation of antigen processing and presentation in MHCII complexes

The mechanism by which interferon regulatory factor 8 (IRF8) mutation contributes to lymphomagenesis is unknown. We modeled IRF8 variants in B cell lymphomas and found that they affected the expression of regulators of antigen presentation. Expression of IRF8 mutants in murine B cell lymphomas suppressed CD4, but not CD8, activation elicited by antigen presentation and downmodulated CD74 and human leukocyte antigen (HLA) DM, intracellular regulators of antigen peptide processing/loading in the major histocompatibility complex (MHC) II. Concordantly, mutant IRF8 bound less efficiently to the promoters of these genes. Mice harboring IRF8 mutant lymphomas displayed higher tumor burden and remodeling of the tumor microenvironment, typified by depletion of CD4, CD8, and natural killer cells, increase in regulatory T cells and T follicular helper cells. Deconvolution of bulk RNA sequencing data from IRF8-mutant human diffuse large B cell lymphoma (DLBCL) recapitulated part of the immune remodeling detected in mice. We concluded that IRF8 mutations contribute to DLBCL biology by facilitating immune escape.

High efficacy of huCD20-targeted AcTaferon in humanized patient derived xenograft models of aggressive B cell lymphoma

Type I interferon (IFN) is a potent antitumoral drug, with an important history in the treatment of hematologic malignancies. However, its pleiotropic nature leads to severe dose-limiting toxicities that blunt its therapeutic potential. To achieve selective targeting of specific immune or tumor cells, AcTakines (Activity-on-Target Cytokines), i.e., immunocytokines utilizing attenuated cytokines, and clinically optimized A-Kines™ were developed. In syngeneic murine models, the CD20-targeted murine IFNα2-based AcTaferons (AFNs) have demonstrated clear antitumoral effects, with excellent tolerability. The current study explores the antitumoral potential of the humanized huCD20-Fc-AFN in 5 different humanized patient derived xenograft (PDX) models of huCD20+ aggressive B non-Hodgkin lymphomas (B-NHLs). The huCD20-Fc-AFN consists of a huCD20-specific single-domain antibody (VHH) linked through a heterodimeric 'knob-in-hole' human IgG1 Fc molecule to an attenuated huIFNα2 sequence. An in vitro targeting efficacy of up to 1.000-fold could be obtained, without detectable in vivo toxicities, except for selective (on-target) and reversible B cell depletion. Treatment with huCD20-Fc-AFN significantly increased the median overall survival (mOS) in both non-humanized (mOS 31 to 45 days; HR = 0.26; p = 0.001), and humanized NSG/NOG mice (mOS 34 to 80 days; HR = 0.37; p < 0.0001). In humanized mice, there was a trend for increased survival when compared to equimolar rituximab (mOS 49 to 80 days; HR = 0.73; p = 0.09). The antitumoral effects of huCD20-Fc-AFN were partly due to direct effects of type I IFN on the tumor cells, but additional effects via the human immune system are essential to obtain long-term remissions. To conclude, huCD20-Fc-AFN could provide a novel therapeutic strategy for huCD20-expressing aggressive B-NHLs.

FAP is a prognostic marker, but not a viable therapeutic target for clinical translation in HNSCC

PURPOSE

PD-1 targeted immunotherapy has imparted a survival benefit to advanced head and neck squamous cell carcinoma (HNSCC), but less than 20% patients produce a durable response to this therapy. Here we aimed to investigate the potential biomarkers for predicting the clinical outcome and resistance to PD-1 targeted immunotherapy in HNSCC patients, and to examine the involvement of FAP+ cancer-associated fibroblasts (CAFs).

METHODS

Bioinformatics methods were applied to analyze multiple datasets and explore the role of PD-1 and FAP in HNSCC. Immunohistochemistry was used to detect the expression of FAP protein. Fap gene knockout mice (Fap-/-) and L929 cells with different levels of Fap overexpression (L929-Fap-Low/High) were established to demonstrate the role of FAP+ CAFs in tumor development and immune checkpoint blockade (ICB) resistance.

RESULTS

The expression level of PD-1 gene was positively correlated with better overall survival and therapeutic response to PD-1 blockade in HNSCC, but not all tumors with high expression of both PD-1 and PD-L1 were responsive. Moreover, FAP gene was overexpressed in pan-cancer tissues, and could serve as a prognostic biomarker for several cancers, including HNSCC. However, FAP protein was undetectable in mouse MTCQ1 tumors and barely expressed in human HNSCC tumors. Furthermore, FAP+ CAFs did not promote tumor growth or enhance the resistance to PD-1 inhibitor treatment.

CONCLUSION

Although FAP+ CAFs have attracted increasing attention for their role in cancer, the feasibility and efficacy of FAP-targeting therapies for HNSCC remain doubtful.

IRF8-mutant B cell lymphoma evades immunity through a CD74-dependent deregulation of antigen processing and presentation in MHC CII complexes

In diffuse large B-cell lymphoma (DLBCL), the transcription factor IRF8 is the target of a series of potentially oncogenic events, including, chromosomal translocation, focal amplification, and super-enhancer perturbations. IRF8 is also frequently mutant in DLBCL, but how these variants contribute to lymphomagenesis is unknown. We modeled IRF8 mutations in DLBCL and found that they did not meaningfully impact cell fitness. Instead, IRF8 mutants, mapping either to the DNA-binding domain (DBD) or c-terminal tail, displayed diminished transcription activity towards CIITA, a direct IRF8 target. In primary DLBCL, IRF8 mutations were mutually exclusive with mutations in genes involved in antigen presentation. Concordantly, expression of IRF8 mutants in murine B cell lymphomas uniformly suppressed CD4, but not CD8, activation elicited by antigen presentation. Unexpectedly, IRF8 mutation did not modify MHC CII expression on the cell surface, rather it downmodulated CD74 and HLA- DM, intracellular regulators of antigen peptide processing/loading in the MHC CII complex. These changes were functionally relevant as, in comparison to IRF8 WT, mice harboring IRF8 mutant lymphomas displayed a significantly higher tumor burden, in association with a substantial remodeling of the tumor microenvironment (TME), typified by depletion of CD4, CD8, Th1 and NK cells, and increase in T-regs and Tfh cells. Importantly, the clinical and immune phenotypes of IRF8-mutant lymphomas were rescued in vivo by ectopic expression of CD74. Deconvolution of bulk RNAseq data from primary human DLBCL recapitulated part of the immune remodeling detected in mice and pointed to depletion of dendritic cells as another feature of IRF8 mutant TME. We concluded that IRF8 mutations contribute to DLBCL biology by facilitating immune escape.

Harnessing type I interferon-mediated immunity to target malignant brain tumors

Type I interferons have long been appreciated as a cytokine family that regulates antiviral immunity. Recently, their role in eliciting antitumor immune responses has gained increasing attention. Within the immunosuppressive tumor microenvironment (TME), interferons stimulate tumor-infiltrating lymphocytes to promote immune clearance and essentially reshape a "cold" TME into an immune-activating "hot" TME. In this review, we focus on gliomas, with an emphasis on malignant glioblastoma, as these brain tumors possess a highly invasive and heterogenous brain TME. We address how type I interferons regulate antitumor immune responses against malignant gliomas and reshape the overall immune landscape of the brain TME. Furthermore, we discuss how these findings can translate into future immunotherapies targeting brain tumors in general.

Therapeutic antibodies for precise cancer immunotherapy: current and future perspectives

Antibodies, as one of the most important components of host adaptive immune system, play an important role in defense of infectious disease, immune surveillance, and autoimmune disease. Due to the development of recombinant antibody technology, antibody therapeutics become the largest and rapidly expanding drug to provide major health benefits to patients, especially for the treatment of cancer patients. Many antibody-based therapeutic strategies have been developed including monoclonal antibodies, antibody-drug conjugates, bispecific and trispecific antibodies and pro-antibodies with promising results from both clinical and pre-clinical trials. However, the response rate and side-effect still vary between patients with undefined mechanisms. Here, we summarized the current and future perspectives of antibody-based cancer immunotherapeutic strategies for designing next-generation drugs.

Type I IFNs repolarized a CD169+ macrophage population with anti-tumor potentials in hepatocellular carcinoma

Macrophages constitute a major component in human hepatocellular carcinoma (HCC) and perform various functions to facilitate disease progression. Reprogramming or reconstituting the tumor surveillance phenotypes of macrophages represents an attractive immunotherapeutic strategy in cancer treatments. The current study identified CD169 as a potential target for macrophage repolarization since it signified a population of macrophages positively correlated with an activated immune signature and better prognosis of patients with HCC. In vitro experiments revealed that a low dose of type I interferon (IFN) could effectively reprogram human monocyte-derived macrophages to upregulate CD169 expression, and such induced CD169⁺ macrophages exhibited significantly enhanced phagocytotic and CD8⁺ T cell-activating capacities compared to controls. A low dose of IFNα also inhibited hepatoma growth in mice in vivo, presumably through polarizing the CD169⁺ macrophage population and enhancing CD8⁺ T cell activities. Notably, IFNα also induced substantial PD-L1 expression on macrophages in vivo, and thus blockade of PD-L1 could further increase the anti-tumor efficacy of IFNα in the treatment of HCC. We propose a low dose of IFNα in combination with a PD-L1 blocking agent as a potential anti-tumor therapeutic strategy via its effects on macrophage polarization.

Next-generation cytokines for cancer immunotherapy

Most studies focus on the first and second signals of T cell activation. However, the roles of cytokines in immunotherapy are not fully understood, and cytokines have not been widely used in patient care. Clinical application of cytokines is limited due to their short half-life in vivo, severe toxicity at therapeutic doses, and overall lack of efficacy. Several modifications have been engineered to extend their half-life and increase tumor targeting, including polyethylene glycol conjugation, fusion to tumor-targeting antibodies, and alteration of cytokine/cell receptor-binding affinity. These modifications demonstrate an improvement in either increased antitumor efficacy or reduced toxicity. However, these cytokine engineering strategies may still be improved further, as each strategy poses advantages and disadvantages in the delicate balance of targeting tumor cells, tumor-infiltrating lymphocytes, and peripheral immune cells. This review focuses on selected cytokines, including interferon-α, interleukin (IL)-2, IL-15, IL-21, and IL-12, in both preclinical studies and clinical applications. We review next-generation designs of these cytokines that improve half-life, tumor targeting, and antitumor efficacy. We also present our perspectives on the development of new strategies to potentiate cytokine-based immunotherapy.

Systemic clinical tumor regressions and potentiation of PD1 blockade with in situ vaccination

Indolent non-Hodgkin's lymphomas (iNHLs) are incurable with standard therapy and are poorly responsive to checkpoint blockade. Although lymphoma cells are efficiently killed by primed T cells, in vivo priming of anti-lymphoma T cells has been elusive. Here, we demonstrate that lymphoma cells can directly prime T cells, but in vivo immunity still requires cross-presentation. To address this, we developed an in situ vaccine (ISV), combining Flt3L, radiotherapy, and a TLR3 agonist, which recruited, antigen-loaded and activated intratumoral, cross-presenting dendritic cells (DCs). ISV induced anti-tumor CD8⁺ T cell responses and systemic (abscopal) cancer remission in patients with advanced stage iNHL in an ongoing trial ( NCT01976585 ). Non-responding patients developed a population of PD1⁺CD8⁺ T cells after ISV, and murine tumors became newly responsive to PD1 blockade, prompting a follow-up trial of the combined therapy. Our data substantiate that recruiting and activating intratumoral, cross-priming DCs is achievable and critical to anti-tumor T cell responses and PD1-blockade efficacy.

Targeting IFNα to tumor by anti-PD-L1 creates feedforward antitumor responses to overcome checkpoint blockade resistance

Many patients remain unresponsive to intensive PD-1/PD-L1 blockade therapy despite the presence of tumor-infiltrating lymphocytes. We propose that impaired innate sensing might limit the complete activation of tumor-specific T cells after PD-1/PD-L1 blockade. Local delivery of type I interferons (IFNs) restores antigen presentation, but upregulates PD-L1, dampening subsequent T-cell activation. Therefore, we armed anti-PD-L1 antibody with IFNα (IFNα-anti-PD-L1) to create feedforward responses. Here, we find that a synergistic effect is achieved to overcome both type I IFN and checkpoint blockade therapy resistance with the least side effects in advanced tumors. Intriguingly, PD-L1 expressed in either tumor cells or tumor-associated host cells is sufficient for fusion protein targeting. IFNα-anti-PD-L1 activates IFNAR signaling in host cells, but not in tumor cells to initiate T-cell reactivation. Our data suggest that a next-generation PD-L1 antibody armed with IFNα improves tumor targeting and antigen presentation, while countering innate or T-cell-driven PD-L1 upregulation within tumor.

Despite the presence of tumor-infiltrating lymphocytes, many patients do not respond to PD-L1/PD-1 blockade therapy. Here they show that PD-L1 antibody armed with interferon-α (IFNα) improves tumor targeting and antigen presentation while countering innate or T-cell-drive PD-L1 upregulation, and overcomes resistance to checkpoint blockade therapy.

Targeting tumor cells with antibodies enhances anti-tumor immunity

Tumor-targeting antibodies were initially defined as a group of therapeutic monoclonal antibodies (mAb) that recognize tumor-specific membrane proteins, block cell signaling, and induce tumor-killing through Fc-driven innate immune responses. However, in the past decade, ample evidence has shown that tumor-targeting mAb (TTmAb) eradicates tumor cells via activation of cytotoxic T cells (CTLs). In this review, we specifically focus on how TTmAbs induce adaptive anti-tumor immunity and its potential in combination therapy with immune cytokines, checkpoint blockade, radiation, and enzyme-targeted small molecule drugs. Exploring the mechanisms of these preclinical studies and retrospective clinical data will significantly benefit the development of highly efficient and specific TTmAb-oriented anti-tumor remedies.